Israel hit the terror group Hezbollah with an all-out air offensive on Monday, in what Lebanese officials called the deadliest day for the country in nearly 20 years — killing nearly 500 people and wounding more than 1,500.

The latest blistering attack on 300 Hezbollah targets by Israel Defense Forces comes after its military chiefs vowed tougher actions against the Iran-backed militant organization, which has been amping up its own assaults on the Jewish state.

The IDF said its objective was to destroy Hezbollah’s capability to attack Israel — targeting the group’s leaders and its missile stockpiles. The ultimate goal is to finally allow thousands of evacuated Israelis to return to their homes in in the north of the country following months of protests from the evacuees.  

Monday’s strike by Israel also was the first time in the deadly back-and-forth – which began when Hezbollah started firing at Israel on Oct. 8 – that the Israeli military issued a warning in southern Lebanon for residents to evacuate in the face of “extensive strikes.” 

In response to the missiles, Hezbollah fired a series of long-range projectiles from Lebanon — another first in the conflict, according to the Israeli military. The terror group also fired dozens of medium-range rockets at northern Israel.  

The IDF said its airstrikes were specifically aimed at taking out Hezbollah rocket facilities after the terror group’s attack Sunday saw around 150 rockets, missiles and drones fired at Israel. 

“If you are in a building housing weapons for Hezbollah, move away from the village until further notice,” read Israel’s warning message Monday to Lebanon’s civilians, according to Lebanese media.

Rather than being a preemptive strike like previous attacks on Hezbollah launchers, an analysis by the Institute for the Study of War suggested the primary goal of Monday’s attack was to “degrade Hezbollah forces.” 

An Israeli official claimed that the attacks would continue unless Hezbollah agrees to a cease-fire. 

“We are going to hit them hard,” the official told The Times of Israel, “but we will stop if they decide it’s time to move toward negotiations.”

Last week, the group has suffered major blows to its leadership and rank-and-file operatives when thousands of booby-trapped pagers and radios exploded in two days of attacks that stunned the world. 

Following Monday’s airstrikes, the US announced it was sending additional troops to the Middle East and urging Americans to leave Lebanon. 

The unknown number of forces would join the 40,000 troops already in the region, according to the Pentagon, as war threatens to engulf the Middle East. 

The State Department has also urged US citizens in Lebanon to seek out ways to leave the volatile country while transportation options remain.

“Due to the unpredictable nature of ongoing conflict between Hezbollah and Israel and recent explosions throughout Lebanon, including Beirut, the US Embassy urges US citizens to depart Lebanon while commercial options still remain available,” the State Department said in an updated advisory.

As the airstrikes unfolded, reports quickly emerged of a mass exodus in Lebanon where Israel launched its airstrikes, with AP reporters noting that some of the missiles went far beyond the border area. 

One of the airstrikes allegedly hit the northeastern regions of Baalbek and Hermel, where a shepherd was killed along with two relatives, according to Lebanon’s state-run National News Agency. 

Another missile hit a forested area in the central province of Byblos, about 81 miles north of the border, the first time in the conflict that an Israeli missile reached the province. 

The Lebanese Health Ministry slammed the latest series of strikes as a sign that Israel was “expanding aggression on Lebanon.”  

Lebanon’s information minister, Ziad Makary, added that the evacuation warnings from Israel were tantamount to “psychological war” on the Lebanese people. 

IDF spokesman Rear Adm Daniel Hagari stood by the airstrikes, claiming that video of secondary explosions after the blasts were evidence enough that the missiles did in fact hit Hezbollah weapons depots. 

“Every home we struck, there are rockets, drones, missiles, which were intended to kill Israeli civilians,” Hagari said.

The daily strikes between the IDF and Hezbollah have caused tens of thousands of people to flee northern Israel and southern Lebanon, with the attacks intensifying in recent weeks.  

The battles have resulted in the deaths of 22 IDF soldiers and 26 Israeli civilians, along with 506 Hezbollah operatives, according to officials from both nations. 

The conflict between Israel and Hezbollah reached a boiling point after thousands of pagers, radios and other electronic devices used by members of the terror group detonated last week in attacks that were blamed on Israel. 

After a series of retaliatory missile strikes from the terror group, Israel launched  an airstrike Friday that killed 16 senior commanders and Hezbollah operatives as they were allegedly meeting to  plan an Oct.7-style invasion in northern Israel, according to the IDF. 

As both sides claimed to be ready for all-out war to break out between them, White House National Security spokesman John Kirby told ABC’s “This Week” on Sunday that US and mediators in the region are working to avoid such an outcome.

“We all, of course, recognize that the tensions are much higher now than they were even just a few days ago,” Kirby said. 

“We want to make sure that we can continue to do everything we can to try to prevent this from becoming an all-out war there with Hezbollah across that Lebanese border.”

With Post wires